Answer:
 (1)
 (1)      
t-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".  
And since we are conducting a lower unilateral lest  then we expected that the value for the statistic would be negative. And the correct answer would be:
b. must be negative
Step-by-step explanation:
Data given and notation      
 represent the sample mean
 represent the sample mean    
 represent the standard deviation for the sample
 represent the standard deviation for the sample      
 sample size
 sample size      
 represent the value that we want to test
 represent the value that we want to test    
 represent the significance level for the hypothesis test.
 represent the significance level for the hypothesis test.    
t would represent the statistic (variable of interest)      
 represent the p value for the test (variable of interest)
 represent the p value for the test (variable of interest)  
State the null and alternative hypotheses.      
We need to conduct a hypothesis in order to determine if the mean is lower than 150, the system of hypothesis would be:      
Null hypothesis: 
      
Alternative hypothesis: 
      
We don't know the population deviation, so for this case is better apply a t test to compare the actual mean to the reference value, and the statistic is given by:      
 (1)
 (1)      
t-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".  
And since we are conducting a lower unilateral lest  then we expected that the value for the statistic would be negative. And the correct answer would be:
b. must be negative